The short answer: SAE 10W-40 motorcycle oil that meets API SG/CF is appropriate, and in this model the engine oil typically also lubricates the transmission. For hot conditions, 20W-50 can be used; for very cold conditions, 5W-40 is sometimes considered acceptable. Always verify with the original owner's or service manual for exact specifications and capacity.
The 1987 Honda FourTrax 350 is an early FourTrax model with a four-stroke, air‑cooled engine. In this vintage setup, Honda guidelines emphasize a standard viscosity and API service class compatible with a wet-clutch layout. Oils that do not meet these specs can affect clutch performance and engine wear over time. The following overview summarizes the oil type, viscosity choices, and maintenance considerations drawn from era manuals and rider references.
Oil requirements and specifications
Below is a concise guide to the oil types and viscosity ranges commonly associated with the 1987 FourTrax 350, including how the oil integrates with the transmission.
- Engine oil viscosity and type: SAE 10W-40 motorcycle oil. Choose an oil that complies with API SG/CF (older standard) or API SH/CF as appropriate for compatibility with a wet-clutch four-stroke engine.
- Climate-based viscosity options: 10W-40 is the baseline. In hot conditions, 20W-50 may be used; in very cold conditions, 5W-40 is sometimes acceptable, though 10W-40 remains the typical recommendation for most climates.
- Transmission/gearbox lubrication: In this model, the transmission is lubricated by the same engine oil (no separate gearbox oil is required). Use the same oil grade across the engine and transmission unless the service manual specifies otherwise.
- Oil capacity and fill level: Consult the service manual for the exact capacity and fill procedure. After a thorough warm-up, fill to the specified level to avoid overfill or underfill, which can affect performance.
- Oil change interval notes: For vintage Hondas, oil and filter changes are commonly recommended every 50–100 operational hours or at least yearly, whichever comes first. Follow the manual’s guidance for your specific bike if available.
In practical terms, the oil you choose should align with these guidelines while also matching your riding environment and maintenance schedule. The engine oil double-serves the transmission in this model, so selecting a suitable grade is important for overall longevity.
Practical tips and considerations
Synthetic vs mineral oil
Both mineral and modern synthetic motorcycle oils that meet the API SG/CF standard can be suitable for this vintage engine. If you ride in extreme temperatures or want potentially longer intervals between changes, a high-quality motorcycle oil rated for wet-clutch operation is advisable. Avoid oils that do not meet the API SG/CF specification.
Brand and availability notes
Common brands that offer compatible 10W-40 motorcycle oils include Honda GN4 10W-40, Motul, Castrol, and Amsoil, among others. When shopping, verify the label for API SG/CF compliance and ensure the product is suitable for older, air-cooled four-stroke engines with a wet clutch.
Summary: For a 1987 Honda FourTrax 350, use SAE 10W-40 motorcycle oil that meets API SG/CF; the engine oil typically also lubricates the transmission. Climate can influence viscosity choices (10W-40 standard, with 20W-50 for heat and 5W-40 for cold conditions), but always confirm exact capacity and maintenance intervals with the original manual.